Inflation, cold dark matter, and the central density problem

A problem with high central densities in dark halos has arisen in the context of LCDM cosmologies with scale-invariant initial power spectra. Although n=1 is often justified by appealing to the inflation scenario, inflationary models with mild deviations from scale-invariance are not uncommon and models with significant running of the spectral index are plausible. Even mild deviations from scale-invariance can be important because halo collapse times and densities depend on the relative amount of small-scale power. We choose several popular models of inflation and work out the ramifications for galaxy central densities. For each model, we calculate its COBE-normalized power spectrum and deduce the implied halo densities using a semi-analytic method calibrated against N-body simulations. We compare our predictions to a sample of dark matter-dominated galaxies using a non-parametric measure of the density. While standard n=1, LCDM halos are overdense by a factor of 6, several of our example inflation+CDM models predict halo densities well within the range preferred by observations. We also show how the presence of massive (0.5 eV) neutrinos may help to alleviate the central density problem even with n=1. We conclude that galaxy central densities may not be as problematic for the CDM paradigm as is sometimes assumed: rather than telling us something about the nature of the dark matter, galaxy rotation curves may be telling us something about inflation and/or neutrinos. An important test of this idea will be an eventual consensus on the value of sigma_8, the rms overdensity on the scale 8 h^-1 Mpc. Our successful models have values of sigma_8 approximately 0.75, which is within the range of recent determinations. Finally, models with n>1 (or sigma_8 > 1) are highly disfavored.Comment: 13 pages, 6 figures. Minor changes made to reflect referee's Comments, error in Eq. (18) corrected, references updated and corrected, conclusions unchanged. Version accepted for publication in Phys. Rev. D, scheduled for 15 August 200

Infrared and ultraviolet cutoffs of quantum field theory

Quantum gravity arguments and the entropy bound for effective field theories proposed in PRL 82, 4971 (1999) lead to consider two correlated scales which parametrize departures from relativistic quantum field theory at low and high energies. A simple estimate of their possible phenomenological implications leads to identify a scale of around 100 TeV as an upper limit on the domain of validity of a quantum field theory description of Nature. This fact agrees with recent theoretical developments in large extra dimensions. Phenomenological consequences in the beta-decay spectrum and cosmic ray physics associated to possible Lorentz invariance violations induced by the infrared scale are discussed. It is also suggested that this scale might produce new unexpected effects at the quantum level.Comment: 5 pages, no figures; general discussion improved, main results unchanged. Version to appear in PR

Organization of freelancers training to process economic information

Hiring freelancers significantly reduces the general costs: economic costs – payment for just specific work done, hours of work – the contractor is interested in the fastest execution of the order, consumer costs – the freelancer is self-sustainable, energy costs – the contractor is interested in energy saving. The stream of processed economic information is changing its quality. The exchange of structured data itself, being externally organized by the freelancers’ efforts, significantly reduces operational (including transactional) costs